JPH025468B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coating method. Conventionally, resin coatings have been applied to the surfaces of various articles for the purpose of surface protection and aesthetics, or for the purpose of electrical shielding. Such coatings can be easily formed by applying paint to the article. Application methods include dipping, spraying,
Although there are various methods such as roll coating and brush coating, dip coating is advantageous for producing a coating film as uniform as possible. However, there are significant obstacles to forming highly uniform coatings by dipping methods. When a member to be coated having a certain volume is immersed in paint, the liquid level of the paint rises and falls when the member is pulled up. As a result, if the boundary line between the inner wall of the container containing the paint and the liquid level of the paint fluctuates up and down, the liquid level will rise (i.e., the boundary line will move upward).
The paint adhering to the inner wall during this process is dried (though not completely dry) while the liquid level is falling (i.e., the boundary line moves downward), and when the liquid level rises again, it dries (though not completely dry) and forms a lump. As a result, it is mixed into the paint by peeling off. If these lumps are mixed into the coating film, a coating film that is uniform in thickness and physical properties cannot be obtained. Another reason is that the thickness of the coating film is influenced by the speed at which the member to be coated is pulled up from the paint; the faster the pulling speed is, the thicker the coating film becomes. Therefore, if the liquid level of the paint fluctuates downward when pulling up the member to be coated, it becomes practically difficult to maintain a constant pulling speed. In order to solve these problems, the container containing the paint should be made very large so that the range of vertical fluctuations in the liquid level can be ignored.
Alternatively, it is possible to constantly overflow a large amount of paint so that no fluctuations in the liquid level appear, but in the former method, the amount of paint to be handled is extremely large, and it is difficult to keep it at a constant composition. In addition, the latter method requires a large amount of paint to overflow without causing fluctuations in the paint level, and prevents rubber from getting mixed in. This turbulence in the paint flow is caused by the formation of a large flow with more paint overflow when the application member is immersed, and a smaller flow with less paint overflow when the application member is pulled up. This will reduce the uniformity of the coating film. SUMMARY OF THE INVENTION The main object of the present invention is to provide a coating method which can prevent the above-mentioned disadvantages, namely, non-uniformity of the coating film due to fluctuations in the liquid level of the coating material during the coating operation. The coating method according to the present invention is characterized in that, in parallel with the operation of immersing the member to be coated in the paint and pulling it up, the balancing member for preventing fluctuations in the liquid level of the paint is relatively moved up and down. be. That is, in the coating method according to the present invention, a coating film having high precision and uniformity can be formed by immersing and pulling up a balancing member in addition to the member to be coated to prevent fluctuations in the liquid level. Further, in the coating method according to the present invention, fluctuations in the liquid level of the paint are prevented by dipping and pulling up the balance member, so that fluctuations in the liquid level can be easily and reliably prevented. As the balance member, one having the same shape as the member to be coated is most preferably used. By having the same shape as the member to be coated, the balance member can be simply operated relative to the member to be coated, i.e., when the member to be coated is immersed, the balance member is pulled up and the member to be coated is pulled up. Fluctuations in the paint level can sometimes be prevented by immersing the balance member. Further, in the case of the same shape, when the balance member itself is also used as the member to be coated, it is even more effective because the coating process can be applied to two members to be coated at the same time. Note that the same shape as used herein means that the volume of the portion of the balance member immersed in the paint is the same as the volume of the portion of the member to be coated that is immersed, and the external shape may be different. Further, as the balance member, one having a volume different from that of the member to be coated may be used. In this case, the dipping and pulling speed of the balance member may be controlled to prevent liquid level fluctuations. In addition, the pulling speed of the member to be coated is usually 0.5
~50 cm/min, particularly 3~20 cm/min is suitable. Furthermore, in the coating method of the present invention, when coating a large number of members to be coated over a long period of time, it is effective to reflux the coating material in order to maintain a uniform composition of the coating material used. Moreover, when refluxing the paint, overflowing is particularly effective. In this case, if the member to be coated is immersed in the paint and pulled up while the paint is overflowing, and at the same time the overflow of the paint is stopped, the fluctuation of the paint level will occur. The balancing member is moved up and down relative to the member to be coated under conditions where this is prevented. Even when the paint is not overflowing, fluctuations in the paint level have already been prevented by the relative up and down movement of the balance member, so even when paint is supplied from the outside and overflows, the paint level changes. The amount may be constant, and since the liquid flow of the paint in the paint becomes constant, a uniform coating film can be formed. Next, a representative example of the coating method of the present invention is shown in the drawings.
The aspect will be explained. FIG. 1 is a drawing of a coating process in which coating is performed by alternately moving the member to be coated and the balance member.
The member to be coated and the balance member have the same shape. In the figure, 1 is a coating tank and 2 is a paint. A indicates a balance member, and B ₁ and B ₂ indicate members to be coated. Arrows indicate movement of the member to be coated and the balance member, and those without arrows indicate stoppage. The description of each step a to f in FIG. 1 is as follows. a: Dip _B1 into the paint and stop it in advance. A
lower. b: Next, lower A and raise B ₁ at the same speed. c: Application of _B1 completed. While A is stopped while painting, move _B1 further upwards and apply the next new member to be coated _{, B2} .
exchange with. d: Lower B ₂ . e: Raise A and lower B ₂ at the same speed (however, it may be different from the speed in case b). f: Raise A and stop, and also lower B ₂ and stop. FIG. 2 shows each of the steps a to f in FIG. 1 with the time axis shown horizontally and the positions of the member to be coated and the balance member shown vertically. X is the attachment/detachment position of the member to be coated, Y is the liquid level of the paint,
Z indicates the stop position in the coating liquid, broken line B shows the positional displacement of the bottom surface of the member to be coated, and broken line A shows the positional displacement of the bottom surface of the balance member. FIG. 3 is a graph showing the displacement of the positions of the balance member and the member to be coated with respect to time when the member to be coated is used as the balance member A in FIG. Since the balance member is also a member to be coated, the broken line A indicating the positional displacement of the balance member is symmetrical to the broken line B indicating the positional displacement of the coated member. 4 to 7 show a coating mode in which a U-shaped tube-shaped coating tank 3 is used instead of the bucket-shaped coating tank in FIG. 1. By making the coating tank a U-shaped tube, the amount of paint can be reduced. Further, since the distance between the member to be coated and the inner wall of the coating tank can be easily made constant, the uniformity of the coating film is also improved. Figure 4 shows the most basic application mode among these, in which the paint 2 stored in the coating tank 3 is stirred by an agitator 4, and the balance member A and the member to be coated B are mixed.
are relatively moved up and down in the same manner as in FIG. 1, and a coating film 5 is formed on the member B to be coated. Balance member A
The member to be coated may also be used as a member. In this case, the number of coating processes is doubled. FIG. 5 shows a coating mode in which the paint is circulated instead of stirring in FIG. 4, and 6 is a paint inlet and 7 is a paint outlet. FIG. 6 is a further improvement of FIG. 5, and shows a coating mode in which the paint overflows from the upper end of the coating tank. In the case of FIG. 5, the paint on the surface tends to stagnate, but in the case of FIG. 6, a smooth flow of paint can be obtained in this example of the apparatus. In this case, if replenishment from the paint inlet 6 is stopped during coating,
The inflow and overflow of paint is performed while the balancing member is operated so that the flow surface of the paint does not fluctuate due to the vertical movement of the balancing member. 8
9 indicates a receiving tray for overflowing paint, and 9 indicates an outlet. FIG. 7 shows an application mode including a paint circulation system.
The overflowing paint is collected in a recovery tank 16 through a recovery pipe 14, where it is sufficiently stirred by a stirrer 15, and then transferred to a coating tank 3 by a pump 13.
sent to. On the way, the paint is filtered by a filter 12 to remove dust and the like. 10 is a paint saucer, and 11 is a pot. In this way, fluctuations in the paint level are effectively prevented, but in the present invention, it is not always required that there be no fluctuations in the liquid level, and the accuracy of the paint film is Slight fluctuations that do not substantially affect the liquid level can be accepted and can be considered as substantially preventing liquid level fluctuations. Various types of articles can be arbitrarily employed as the member to be coated, and a typical example thereof is an image holding member used in electrophotography. The image holding member has an insulating layer or a photoconductive layer on its surface, and the uniformity of these layers significantly affects the image forming ability. Therefore, the coating method according to the present invention is most effectively applied. This is one possible example. Image holding members on which electrostatic images or toner images are formed by electrophotography include image holding members having a photoconductive layer and image holding members not having a photoconductive layer, which are called electrophotographic photoreceptors. It consists of a support and an image-retaining layer on it. Electrophotographic photoreceptors have various configurations in order to obtain predetermined characteristics or depending on the type of electrophotographic process to which they are applied. Typical electrophotographic photoreceptors include photoreceptors in which a photoconductive layer is formed on a support, and photoreceptors in which a photoconductive layer is laminated with an insulating layer thereon, which are widely used. . A photoreceptor composed of a support and a photoconductive layer is used for image formation by most common electrophotographic processes, ie, charging, image exposure and development, and optionally transfer. In addition, the insulating layer in a photoreceptor equipped with an insulating layer is used for purposes such as protecting the photoconductive layer, improving the mechanical strength of the photoreceptor, improving dark decay characteristics, or being applied to a specific electrophotographic process. Typical examples of photoreceptors having such an insulating layer or electrophotographic processes using such a photoreceptor having an insulating layer include, for example,
U.S. Patent No. 2860048, JP 41-16429, JP 38-15446, JP 46-3713, JP 42-23910, JP 43-24748
Publication No. 19747, Special Publication No. 1974, Special Publication No. 1974-
It is described in Publication No. 4121, etc. In addition, there is also an image holding member having only an insulating layer without a photoconductive layer, and some typical uses of this image holding member will be described below. (1) For example, Japanese Patent Publication No. 32-7115, Japanese Patent Publication No. 32-7115,
As described in Japanese Patent Publication No. 8204 and Japanese Patent Publication No. 43-1559, an electrostatic image formed on an electrophotographic photoreceptor without a photoconductive layer is used for the purpose of improving the repeatability of the electrophotographic photoreceptor. The toner image is transferred to an image holding member and developed, and then the toner image is transferred to a recording medium. An image holding member used in this electrophotographic process. (2) In addition, as another electrophotographic process in which an electrostatic image is formed on an image holding member without a photoconductive layer in correspondence with an electrostatic image formed on an electrophotographic photoreceptor, for example, Japanese Patent Publication No. 45-30320 Publication No., Tokukosho
As described in Japanese Patent Application Laid-open No. 48-5063 and Japanese Patent Application Laid-Open No. 51-341, an electrostatic image is formed on a screen-shaped electrophotographic photoreceptor having a large number of fine openings by a predetermined electrophotographic process. By applying corona charging to an image holding member without a photoconductive layer through this electrostatic image, the ion flow of the corona is modulated and the electrostatic image is transferred to an image holding member without a photoconductive layer. An example of this process is to form an image, develop it with toner, and transfer it to a recording medium to form a final image. Examples include image holding members used in this electrophotographic process. A typical structure of an electrophotographic photoreceptor having an insulating layer is a support made of copper, stainless steel, aluminum, etc.
It is a laminate including a photoconductive layer and an insulating layer. The photoconductive layer is ZnO, CdS, CdSe, _Tio2 , ZnS,
Formed by bonding, vapor deposition, sputtering, coating, etc. of organic semiconductors such as ZnSe, Se, Se-Te, Se-Te-AS, or polyvinyl carbazole, alone or together with a binder resin. . The thickness of the photoconductive layer depends on the type and characteristics of the photoconductive material used, but is generally 5 to 100μ, particularly 10 to 50μ.
degree is suitable. In general, when an insulating layer is attached for the main purpose of protecting the photoconductive layer, improving its durability, dark decay characteristics, etc., the insulating layer is set relatively thin. The layer is set relatively thick. Usually, the thickness of the insulating layer is 5 to 70μ, especially 10 to 70μ.
Set to 50μ. As the binder resin of the photoconductive layer and the resin used to form the insulating layer, various ordinary insulating resins can be used as appropriate. Examples include polyethylene, polyester, polypropylene, polystyrene, polyvinyl chloride, polyvinyl acetate, acrylic resin, polycarbonate, silicone resin, fluororesin, and epoxy resin. Example 1 Coating was carried out by the method shown in FIG. However, in the diagram
A member to be coated was also used as _A1 . First, a paint was prepared by uniformly dissolving polyvinylcarbazole (trade name: PVK, manufactured by BASF), monochlorobenzene, and trinitrofluorenone (TNF) in a ratio (weight ratio) of 10:5:10. Also, as a member to be coated, the outer diameter is 80mm and the length is 300mm.
An aluminum cylinder with a wall thickness of 4 mm was used. Then, the coating operation was performed according to FIG. That is, FIGS. 3a to 3f show the coating process when two coated members are coated alternately (that is, one coated member is given the role of a balancing member). Further, FIG. 4 schematically shows the vertical positional relationship of the members to be coated corresponding to each step in FIG. 3. The coating process will be explained according to FIG. a... First, submerge one cylinder into the paint, and then lower the other cylinder to the liquid level. Next, b...lower the other cylinder into the paint and raise one cylinder at almost the same speed (10 cm/min). c...One cylinder completes application and continues to rise (switching to high speed of 100 cm/min); the other cylinder remains stationary in the paint. d...One cylinder is replaced with a new one at a fixed position above, and then lowered to the liquid level at a speed of 100 cm/min. During this time, the other cylinder remains stopped. The other cylinder is coated in the same process as e...b. Coating of the other cylinder is completed in the same process as f...c. The coated member coated in this way was heated to 100°C.
Dry for 20 minutes. The film thickness at this time was 7μ. A photoreceptor was manufactured in this manner. As a comparison sample, a sample was prepared which was coated and dried using the same coating equipment, paint, and coating conditions without using a balancing member (A in the case of FIG. 1). In this case, as a matter of course, the liquid level of the paint rises when the application member descends, and decreases when the application member ascends. For this reason, even when the surface of the photoreceptor coating was visually compared, disturbances such as coating unevenness and sagging were observed in the comparison sample. On the other hand, in the photoreceptor prepared by the method of the present invention, no disturbance was observed on the surface of the coating film. The two samples mentioned above were subjected to a process consisting of (i) charging (5.7 KV), (ii) image exposure (25 Lux sec), (iii) development (magnetic brush method), (iv) transfer charging 5.4 KV, and (v) brush cleaning. When evaluating the image output using a method, it was found that the comparative sample had image disturbances corresponding to disturbances on the coated surface, but no image disturbances were observed in the photoreceptor prepared according to the present invention. Ta. Example 2 The coating method shown in FIG. 7 was used. That is, the coating tank 3 was formed into a U-shaped tube, and the coating material was coated while circulating the paint by overflowing from the upper end of the coating tank. Since the coating tank is a U-shaped tube, the flow of the paint is uniform, and there is an overflow, which has the advantage that the surface of the coating liquid is constantly refreshed. Furthermore, changes in viscosity due to solvent evaporation were compensated for by adding solvent little by little to the recovered paint. Further, dust and the like mixed into the paint were removed by a filter 12. In this example, 20 photoreceptors were made in succession using the same paint and material to be coated as in Example 1, and for comparison, a comparative sample made in Example 1 was also made in succession. I created 20 books. The table below shows the results of comparing the 1st and 20th samples of each sample.

[Table] As described above, the coating film of the photoreceptor obtained in this example was uniform, and even when an image was formed, a clear image was obtained.

[Brief explanation of drawings]

FIG. 1 shows one embodiment of the coating method according to the present invention, and a, b, c, d, e, and f in FIG. 1 are explanatory diagrams showing each step of the coating operation. FIGS. 2 and 3 are graphs showing changes in the positions of the member to be coated and the balance member over time when the coating method shown in FIG. 1 is carried out. Figure 4, Figure 5,
FIG. 6 and FIG. 7 are explanatory diagrams showing other embodiments of the coating method of the present invention, respectively. A... Balance member, B ₁ and B ₂ ... Member to be coated,
1... Application tank, 2... Paint.

Claims (1)

[Scope of Claims] 1. A coating method characterized by immersing the member to be coated in the paint and pulling it up, and in parallel, relatively moving up and down a balance member to prevent fluctuations in the liquid level of the paint. . 2. If the member to be coated is dipped into the paint and pulled up while the paint is overflowing, and at the same time the overflow of the paint is stopped, fluctuations in the liquid level of the paint are prevented. A coating method characterized in that a balancing member is moved up and down relative to the member to be coated under certain conditions.